Ashtangasamgraha 34.29

34.29

sūcyastisro vṛttā nigūḍhadṛḍhapāśāḥ |

tatra māṃsaleṣvavakāśeṣu tryaṅgulā tryasrā |

sandhyasthivraṇeṣvalpamāṃseṣu ca dvyaṅgulā vṛttā pakvāmāśayayormarmasu ca sārdhadvyaṅgulā dhanurvakrā vrīhimukhā ca ||

The needles (sūcī) are three, circular, and have deeply recessed, strong eyes.

Among them, in fleshy spaces, [the needle] is three fingers long and three-sided;

in ulcers of the joints, bones, and regions of little flesh, it is two fingers long and circular; and in the case of the large and small intestines and vital spots (marman), it is two and a half fingers long, curved like a bow, and has a tip like a grain of rice.